I have search for many hours for answers to questions on new Graphics Cards which require 8pin and 6 pin or 8pin and 8pin power connections aside from the motherboard supplied power and what the appropriate method was to connect the GPU cards to the 8 pin pcie power connections. This is complicated by the fact that the Precisions seem to only have 6pin cables installed with the towers regardless of the power supply that is installed. Yes. Everyone understands hopefully that if you have, for example, a 450 watt power supply ( forget the efficiency aspect of the actual power supply) as I am interested in the mechanics of the design.
The power supply connects to a PC board, which appears to be called "Power Supply extended card"
Now, looking at the connectors on this extended card, there is a "POWER_VGA1" 8pin connection on this extended card (bottom left black socket). To this 8pin connector, on my T5600 and seemingly on all the others that have made similar inquiries, we all have a 8pin male connector that fit into the extended card. My 8pin connector has two sets of wires leaving the connector and becoming two 6 pin connectors, one of which 6pin connectors is plugged into my stock Quadro 5000 video card.
OK. So, now most people are wanting to change out the 6pin Quadro card with either an 8pin or 8 pin plus 6pin or 8pin and 8pin graphics card such as a GTX 980TI or GTX 1080 or GTX 1070 or AMDs similar card.
Having researched the PCIe standard (and please correct me with a reference if I am wrong), the difference between a 6pin PCIe connection and an 8pin PCIe connection is the addition of two more negative wires. The 12v positive wires remain at 3 wires which is the same as the six pin.
On the POWER_VGA1 connection on the Power Supply Extended Card, I already mentioned that it has 8 female terminals. The 8pin male plug only utilizes 6 of those Power Supply Extended Card pins. The pins that are not utilized are pins 7 and 8 --they are empty.
Questions that I and I am certain others, would like answered are:
1) Pin 7 and pin 8 on the Power Supply Extended Card are: a) actually connected to the Negative power; B) not connected to anything and are just dummy pins; or C) some other configuration which do not and cannot be utilized to comply with an 8pin PCIe power requirement. Again we are just talking about the Power Supply Extended Card. Wiring and wire gauge is not relevant at this point. the wattage of the power supply at present is also not relevant at this time.
2) It there a physical or mechanical restriction on the wattage for these computers which can be made available through this POWER_VGA1 connector on the Power Supply Extended Card. Is there something that restricts the wattage available to the POWER_VGA1 connector and creates a maximum wattage that can be delivered through this POWER_VGA1 socket. Up to this point on the circuit, conduit gauge can be considered as the Circuit board itself may actually be limited as to the number of amps that can be drawn through the circuit. Again, do not worry about the actual wattage of the power supply unit or you may consider a hypothetical 10,000 watt supply so that you can see there is not wattage availability restriction on the input side.
3) What is the maximum wattage spec available through the POWER_VGA1 socket. Again, do not consider the power supply as the power supply can be changed out from 450 to 825 to 1100 or 10,000 watts as a hypothetical). Just what is the maximum wattage spec'd for this socket which again would consider the circuitry of the circuit board itself. It is my expectation that the Power Supply Extended Card does not differ between systems ordered with the 450 (or lowest power supply wattage), the 825 watt power supply or the 1100 watt power supply. So there must be a maximum wattage that can be supplied through this connector. If the Power Supply Extended Card does differ between version of the T5600 or T7600, please respond with that information.
4) Does the 8pin socket on the Power Supply Extended Card correspond to the 8pin circuitry requirements of the GPU cards. For example, can someone connect an 8 wire, 8pin male plug (rather than 6 wire that comes with the computer) into the POWER_VGA1 socket and run that 8 wire to the GPU that requires an 8pin input or dual 8pin input.
The results of the above questions may be better able to answer the need of Precision tower owners to know how to correctly install these 8pin GPUs. I myself do not like the idea of using the 6+2 pin adapters which do nothing more than run jumpers from the 6 pin to create an 8 pin. Also the two 6pin to one 8pin for connection to the GPU also do not make much sense as the only thing you are doing by connecting two 6pin to one 8pin is creating a thicker gauge wire. If one creates a wiring harness with thicker gauge wire from the start, answers to the above questions should answer the question as to whether the POWER_VGA1 socket can support two 8-pin 150 watt wiring sets. If the POWER_VGA1 socket can support 300 watts and it is the wiring that needs to be made thicker and / or integrate the pins 7 and 8 on the socket then we can make a harness with thicker gauge wire and / or integrate pins 7 and 8.
If DELL can answer this, then everyone will know what is appropriate for the GPU card they are buying. I know I keep repeating it but the wattage of the Power Supply unit itself is not relevant as the requirements will differ between each card and each computer setup. That is why no reference to the PSU wattage itself is appropriate.
Thanks and I really look forward to anyone with the answers to the above questions.
1) Pin 7 and pin 8 on the do not and cannot be utilized to comply with an 8pin PCIe power requirement. The connector is NOT one to one 8 Pin Straight thru. D92C9 is the connector to 2X 6 pin PCIE power.
2) It there a physical or mechanical restriction on the wattage for these computers which can be made available through this POWER_VGA1 connector on the Power Supply Extended Card.
If you don't want issues Use the 825W power supply.
Dell Precision T5600 825W Power Supply 0DR5JD H825EF-00
3) What is the maximum wattage spec available through the POWER_VGA1 socket.
150W officially. Using D92C9 cable and 825W power supply.
Unofficially you can use this
4) Does the 8pin socket on the Power Supply Extended Card correspond to the 8pin circuitry requirements of the GPU cards.
NO it does not.